The invention relates to a wound heat exchanger with a tube bundle of a plurality of tubes, which are wound around a core tube, and with a cover, which defines an external chamber around the tube.
Natural gas is continuously liquefied in large quantities in LNG baseload systems. Most of the time, liquefaction of natural gas is accomplished by heat exchange with a coolant in wound heat exchangers. However, many other applications of wound heat exchangers are also known.
In a wound heat exchanger, several layers of tubes are spirally wound on a core tube. A tube bundle is formed by this type of tube winding. A wound heat exchanger contains at least one tube bundle, but it may also have two or more tube bundles. A first medium is piped through the inside of at least one portion of the tubes, and this medium exchanges heat with a second medium flowing in the chamber between the tubes and a surrounding cover. The tubes are merged into several groups above and/or below the tube bundle and fed out of the external chamber in a bundled manner using collectors (headers).
These types of wound heat exchanger and their application, for example for liquefaction of natural gas, are described in each of the following publications:    Hausen/Linde, Cryogenic Engineering, 2nd ed., 1985, pages 471-475;    W. Scholz, “Wound Tube Heat Exchangers,” Linde Reports on Science and Technology, No. 33 (1973), pages 34-39;    Kreis, “Wound Heat Exchangers” in Hess, Apparatus Handbook: Technology, Construction, Application, 1990, pages 262-264;    W. Bach, “Offshore Natural Gas Liquefaction with Nitrogen Cold Process Design and Comparison of Wound Tube and Plate Heat Exchangers,” Linde Reports on Science and Technology, No. 64 (1990), pages 31-37;    W. Förg et al., “A New LNG Baseload Process and Manufacturing of the Main Heat Exchanger,” Linde Reports on Science and Technology, No. 78 (1999), pages 3-11 (English version: W. Förg et al., “A New LNG Baseload Process and Manufacturing of the Main Heat Exchanger,” Linde Reports on Science and Technology, No. 61 (1999), pages 3-11);    DE 1501519 A;    DE 1912341 A;    DE 19517114 A;    DE 19707475 A; and    DE 19848280 A.
The invention is based on the objective of reducing acoustic emissions from these types of wound heat exchangers.
This objective is attained by the installation of anti-drumming walls, which are shaped like a cylinder cover or preferably a cylinder cover segment, whereby at least one first anti-drumming wall is arranged on the external side of a first layer of tubes.
The anti-drumming wall prevents or reduces the formation of stationary acoustical waves between the core tube and the container wall. As a result, the noise emission during operation of the heat exchanger can be reduced effectively. An anti-drumming wall differs from walls for guiding flow or for separating chambers, as known from CH 683124 or DE 1501519, in that on a portion of the tangential extension (of the circumference) and/or the axial extension (of the length) of the tube bundle, they are permeable for the fluid flowing in the external chamber.
In this case, the terms “tangential,” “radial” and “axial” refer to the axis of the core tube of the tube bundle.
The anti-drumming wall is comprised preferably of a solid material, for example a metal sheet, plastic plate or a plastic-coated metal sheet.
They must be sufficiently rigid so that they themselves are not excited to produce acoustic vibrations during operation of the heat exchanger. They should not have any holes.
All geometric information such as cylinder shape, conformity of lines and surfaces, etc. are not meant to be understood in a precise mathematical manner, but approximately within the framework of the concrete technical implementation of corresponding components.
The axial extension of the anti-drumming wall is less than the axial extension of the tube bundle. For example, it is less than 80%, preferably less than 50% of the axial extension of the tube bundle. In addition or alternatively, the tangential extension of the anti-drumming wall is less than 360°, in particular less than or equal to 180°, for example less than or equal to 90°. Two or more of these types of anti-drumming walls are preferably arranged tangentially, axially and/or radially offset from one another.
Basically, an anti-drumming wall can also be arranged on the external side of the bundle, preferably, however, between the first tube layer and a second tube layer adjacent to the first. Of course, a combination of external anti-drumming walls and anti-drumming walls arranged in intermediate layers is expedient.
It is advantageous if several cylindrical anti-drumming walls are arranged consecutively in the radial direction in that a first group of anti-drumming walls, which has at least two anti-drumming walls as the first and the second elements respectively, wherein the first element of the first group is arranged between the first and second tube layers and the second element of the first group is arranged between a third and a fourth tube layer adjacent to the third, wherein the axial edges of all elements of the first group lie on the leg surfaces of a first cylinder segment with an angle α, and wherein the axis of the cylinder segment runs on the core tube axis.
As a result of this, the radial spacing of the anti-drumming walls can be coordinated with the wavelength of the noise being dampened.
No anti-drumming wall is preferably arranged within the first cylinder segment between the second and the third tube layers, i.e., one or more tube layers within the cylinder segment are free and make radial fluid exchange in the external chamber possible.
For example, an anti-drumming wall is arranged periodically in every nth tube layer within the cylinder segment, whereby n is greater than 2.
In order to also facilitate the radial exchange of fluid in the external chamber, it is advantageous for the anti-drumming walls to be arranged tangentially and radially offset. For this purpose, a second group of anti-drumming walls is used, which have at least one first element, wherein the axial edges of all elements of the second group lie on the leg surfaces of a second cylinder segment with an angle β, the axis of the second cylinder segment runs on the core tube axis and the first and second cylinder cover segments are essentially disjoint and in particular have precisely one common leg surface. In this connection, one element of the second group in particular is arranged between the second and third tube layers.
The sum of angles α and β is preferably equal to a whole number that is a fractional amount of 360°, at most the angles α and β are preferably equal. As a result, the entire angular area can be covered regularly by anti-drumming walls that are arranged in an offset manner.
Axial bars having guides for the tubes are frequently arranged between two adjacent tube layers. In this case, it is advantageous if at least one anti-drumming wall extends in the tangential direction between two adjacent bars. This is preferably realized in the case of all anti-drumming walls. The bars then define the leg areas of the aforementioned cylinder segments.
The invention also relates to the application of this type of heat exchanger for executing an indirect heat exchange between a hydrocarbonaceous stream and at least one heat fluid or cold fluid.
In this case, the hydrocarbonaceous stream is formed by natural gas, for example.
The hydrocarbonaceous stream is liquefied, cooled, heated and/or vaporized during the indirect heat exchange. The heat exchanger is preferably used for natural gas liquefaction or natural gas vaporization.